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DrX Whiz Niraj
Introduction to Human Body
Welcome to the foundation of medical science! Here we will learn about Anatomy, Physiology, Homeostasis, and the language of the human body.
Anatomy (Structure)
The word Anatomy comes from Greek words Ana (up) and tome (cutting). It is the science that studies the structure of the body and the physical relationships among body parts.
Example: Studying the shape, size, and weight of the human heart.
Physiology (Function)
The word Physiology comes from Physio (nature) and logy (study of). It is the science that studies the functions of body parts—how they work together to sustain life.
Example: Studying how the heart pumps blood to the lungs and the rest of the body.
The human body is highly organized, much like words forming sentences, and sentences forming a book. There are 6 levels of organization from smallest to largest:
Our body consists of 11 principal organ systems that work together to maintain life. (Trick to remember: MURDERS LINC)
| System | Main Organs | Key Function |
|---|---|---|
| Muscular | Skeletal Muscles | Produces movement, generates heat. |
| Urinary | Kidneys, Bladder | Filters blood, eliminates waste as urine. |
| Respiratory | Lungs, Trachea | Exchange of O2 and CO2. |
| Digestive | Stomach, Intestines | Breaks down food, absorbs nutrients. |
| Endocrine | Thyroid, Pituitary Glands | Regulates body via hormones. |
| Reproductive | Testes, Ovaries | Produces gametes for reproduction. |
| Skeletal | Bones, Joints | Provides support and protection. |
| Lymphatic | Spleen, Lymph nodes | Defends against infection and disease. |
| Integumentary | Skin, Hair, Nails | Protects body, regulates temperature. |
| Nervous | Brain, Spinal Cord | Detects and responds to changes (Fast). |
| Cardiovascular | Heart, Blood Vessels | Pumps blood, transports nutrients/oxygen. |
All living human beings have certain characteristics that distinguish them from non-living things. There are 6 basic life processes:
- 1. Metabolism: The sum of all chemical processes in the body. It includes Catabolism (breaking down large molecules into smaller ones) and Anabolism (building up large molecules from smaller ones).
- 2. Responsiveness: The body’s ability to detect and respond to internal or external changes (e.g., pulling hand away from a hot surface).
- 3. Movement: Includes motion of the whole body, individual organs, single cells, and even tiny structures inside cells.
- 4. Growth: An increase in body size resulting from an increase in the size of existing cells, the number of cells, or both.
- 5. Differentiation: The development of a cell from an unspecialized to a specialized state (e.g., Stem cells developing into RBCs).
- 6. Reproduction: The formation of new cells for tissue growth/repair, or the production of a new individual.
Definition of Homeostasis:
Homeostasis is the condition of equilibrium (balance) in the body's internal environment. It is maintained by the body's regulatory processes. Example: Keeping blood glucose levels between 70-110 mg/dL, or body temperature at 37°C.
Homeostasis is controlled by Feedback Systems consisting of 3 components:
Types of Feedback Systems:
- Negative Feedback: Reverses a change in a controlled condition (e.g., Blood pressure regulation, Sweating to cool down). *Most common in body*.
- Positive Feedback: Strengthens or reinforces a change in a controlled condition (e.g., Normal childbirth, Blood clotting).
To describe the human body accurately, scientists use standard terms. The standard reference position is the Anatomical Position (Subject stands erect facing observer, head level, feet flat on floor, arms at sides, palms turned forward).
Directional Terms
- Superior / Inferior: Towards Head / Towards Feet (e.g., Heart is superior to liver).
- Anterior (Ventral) / Posterior (Dorsal): Front / Back (e.g., Sternum is anterior to heart).
- Medial / Lateral: Near midline / Away from midline (e.g., Lungs are lateral to heart).
- Proximal / Distal: Nearer to attachment / Farther from attachment (e.g., Knee is proximal to ankle).
Body Planes and Sections
- Sagittal Plane: Divides the body into right and left sides. (Midsagittal = equal halves).
- Frontal (Coronal) Plane: Divides the body into anterior (front) and posterior (back) portions.
- Transverse (Horizontal) Plane: Divides the body into superior (upper) and inferior (lower) portions.
Clinical Correlation (Applied Physiology)
What happens if Homeostasis fails?
When one or more components of the body lose their ability to contribute to homeostasis, the normal balance is disrupted. If the disruption is moderate, a disease or disorder may occur. If it is severe, it may result in death. Example: Failure to maintain blood sugar homeostasis leads to Diabetes Mellitus.